Painting lichen on terrain

I'm working on few weathered terrain pieces at the moment (basically it's another ruined wall piece) and as part of the weathering I've added some lichen to the rocks.

Here's a picture I took to use as reference:


...and here's the effect in miniature:

I'm pretty pleased with the outcome for is, and it's easy to do:

1- Use PVA glue to stick sand where you want the lichen to be
2- Paint the rock with whatever colour you want, I used grey (about Codex Grey) and then drybrushed with light grey (about Fortress Grey). Make sure you include the sand in your drybrushing
3- Drybrush the lichen with whatever colour you want it to end up as. In my picture above I used Gretchin Green.

Easy, and it adds instant age. Here's the complete terrain piece:

I've also knocked up some bases for these trees, nothing too special with these: